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Last change on this file since f898983 was dd46fd3, checked in by Peter A. Buhr <pabuhr@…>, 3 years ago
generalization of PRNG
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1	//
2	// Cforall Version 1.0.0 Copyright (C) 2020 University of Waterloo
3	//
4	// The contents of this file are covered under the licence agreement in the
5	// file "LICENCE" distributed with Cforall.
6	//
7	// kernel/fwd.hfa -- PUBLIC
8	// Fundamental code needed to implement threading M.E.S. algorithms.
9	//
10	// Author : Thierry Delisle
11	// Created On : Thu Jul 30 16:46:41 2020
12	// Last Modified By :
13	// Last Modified On :
14	// Update Count :
15	//
16
17	#pragma once
18
19	#include "bits/defs.hfa"
20	#include "bits/debug.hfa"
21
22	#ifdef __cforall
23	#include "bits/random.hfa"
24	#endif
25
26	struct thread$;
27	struct processor;
28	struct cluster;
29
30	enum __Preemption_Reason { __NO_PREEMPTION, __ALARM_PREEMPTION, __POLL_PREEMPTION, __MANUAL_PREEMPTION };
31
32	#define KERNEL_STORAGE(T,X) __attribute((aligned(__alignof__(T)))) static char storage_##X[sizeof(T)]
33
34	#ifdef __cforall
35	extern "C" {
36	extern "Cforall" {
37	extern __attribute__((aligned(64))) __thread struct KernelThreadData {
38	struct thread$ * volatile this_thread;
39	struct processor * volatile this_processor;
40	volatile bool sched_lock;
41
42	struct {
43	volatile unsigned short disable_count;
44	volatile bool enabled;
45	volatile bool in_progress;
46	} preemption_state;
47
48	PRNG_STATE_T random_state;
49
50	struct {
51	uint64_t fwd_seed;
52	uint64_t bck_seed;
53	} ready_rng;
54
55	struct __stats_t * volatile this_stats;
56
57	#ifdef __CFA_WITH_VERIFY__
58	// Debug, check if the rwlock is owned for reading
59	bool in_sched_lock;
60	unsigned sched_id;
61	#endif
62	} __cfaabi_tls __attribute__ ((tls_model ( "initial-exec" )));
63
64	extern bool __preemption_enabled();
65
66	static inline KernelThreadData & kernelTLS( void ) {
67	/* paranoid */ verify( ! __preemption_enabled() );
68	return __cfaabi_tls;
69	}
70
71	extern uintptr_t __cfatls_get( unsigned long int member );
72	#define publicTLS_get( member ) ((typeof(__cfaabi_tls.member))__cfatls_get( __builtin_offsetof(KernelThreadData, member) ))
73
74	static inline
75	#ifdef __x86_64__ // 64-bit architecture
76	uint64_t
77	#else // 32-bit architecture
78	uint32_t
79	#endif // __x86_64__
80	__tls_rand() {
81	return PRNG_NAME( kernelTLS().random_state );
82	}
83
84	static inline unsigned __tls_rand_fwd() {
85	return LCGBI_fwd( kernelTLS().ready_rng.fwd_seed );
86	}
87
88	static inline unsigned __tls_rand_bck() {
89	return LCGBI_bck( kernelTLS().ready_rng.bck_seed );
90	}
91
92	static inline void __tls_rand_advance_bck(void) {
93	kernelTLS().ready_rng.bck_seed = kernelTLS().ready_rng.fwd_seed;
94	}
95	}
96
97	extern void disable_interrupts();
98	extern void enable_interrupts( bool poll = false );
99
100	extern "Cforall" {
101	enum unpark_hint { UNPARK_LOCAL, UNPARK_REMOTE };
102
103	extern void park( void );
104	extern void unpark( struct thread$ *, unpark_hint );
105	static inline void unpark( struct thread$ * thrd ) { unpark(thrd, UNPARK_LOCAL); }
106	static inline struct thread$ * active_thread () {
107	struct thread$ * t = publicTLS_get( this_thread );
108	/* paranoid */ verify( t );
109	return t;
110	}
111
112	extern bool force_yield( enum __Preemption_Reason );
113
114	static inline void yield() {
115	force_yield(__MANUAL_PREEMPTION);
116	}
117
118	// Yield: yield N times
119	static inline void yield( size_t times ) {
120	for( times ) {
121	yield();
122	}
123	}
124
125	// Semaphore which only supports a single thread
126	struct single_sem {
127	struct thread$ * volatile ptr;
128	};
129
130	static inline {
131	void ?{}(single_sem & this) {
132	this.ptr = 0p;
133	}
134
135	void ^?{}(single_sem &) {}
136
137	bool wait(single_sem & this) {
138	for() {
139	struct thread$ * expected = this.ptr;
140	if(expected == 1p) {
141	if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
142	return false;
143	}
144	}
145	else {
146	/* paranoid */ verify( expected == 0p );
147	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
148	park();
149	return true;
150	}
151	}
152
153	}
154	}
155
156	bool post(single_sem & this) {
157	for() {
158	struct thread$ * expected = this.ptr;
159	if(expected == 1p) return false;
160	if(expected == 0p) {
161	if(__atomic_compare_exchange_n(&this.ptr, &expected, 1p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
162	return false;
163	}
164	}
165	else {
166	if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
167	unpark( expected );
168	return true;
169	}
170	}
171	}
172	}
173	}
174
175	// Synchronozation primitive which only supports a single thread and one post
176	// Similar to a binary semaphore with a 'one shot' semantic
177	// is expected to be discarded after each party call their side
178	enum(struct thread$ *) { oneshot_ARMED = 0p, oneshot_FULFILLED = 1p };
179	struct oneshot {
180	// Internal state :
181	// armed : initial state, wait will block
182	// fulfilled : wait won't block
183	// any thread : a thread is currently waiting
184	struct thread$ * volatile ptr;
185	};
186
187	static inline {
188	void ?{}(oneshot & this) {
189	this.ptr = oneshot_ARMED;
190	}
191
192	void ^?{}(oneshot &) {}
193
194	// Wait for the post, return immidiately if it already happened.
195	// return true if the thread was parked
196	bool wait(oneshot & this) {
197	for() {
198	struct thread$ * expected = this.ptr;
199	if(expected == oneshot_FULFILLED) return false;
200	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
201	park();
202	/* paranoid */ verify( this.ptr == oneshot_FULFILLED );
203	return true;
204	}
205	}
206	}
207
208	// Mark as fulfilled, wake thread if needed
209	// return true if a thread was unparked
210	thread$ * post(oneshot & this, bool do_unpark = true) {
211	struct thread$ * got = __atomic_exchange_n( &this.ptr, oneshot_FULFILLED, __ATOMIC_SEQ_CST);
212	if( got == oneshot_ARMED \|\| got == oneshot_FULFILLED ) return 0p;
213	if(do_unpark) unpark( got );
214	return got;
215	}
216	}
217
218	// base types for future to build upon
219	// It is based on the 'oneshot' type to allow multiple futures
220	// to block on the same instance, permitting users to block a single
221	// thread on "any of" [a given set of] futures.
222	// does not support multiple threads waiting on the same future
223	enum(struct oneshot *) { future_ARMED = 0p, future_FULFILLED = 1p, future_PROGRESS = 2p, future_ABANDONED = 3p };
224	struct future_t {
225	// Internal state :
226	// armed : initial state, wait will block
227	// fulfilled : result is ready, wait won't block
228	// progress : someone else is in the process of fulfilling this
229	// abandoned : client no longer cares, server should delete
230	// any oneshot : a context has been setup to wait, a thread could wait on it
231	struct oneshot * volatile ptr;
232	};
233
234	static inline {
235	void ?{}(future_t & this) {
236	this.ptr = future_ARMED;
237	}
238
239	void ^?{}(future_t &) {}
240
241	void reset(future_t & this) {
242	// needs to be in 0p or 1p
243	__atomic_exchange_n( &this.ptr, future_ARMED, __ATOMIC_SEQ_CST);
244	}
245
246	// check if the future is available
247	bool available( future_t & this ) {
248	while( this.ptr == future_PROGRESS ) Pause();
249	return this.ptr == future_FULFILLED;
250	}
251
252	// Prepare the future to be waited on
253	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
254	bool setup( future_t & this, oneshot & wait_ctx ) {
255	/* paranoid */ verify( wait_ctx.ptr == oneshot_ARMED \|\| wait_ctx.ptr == oneshot_FULFILLED );
256	// The future needs to set the wait context
257	for() {
258	struct oneshot * expected = this.ptr;
259	// Is the future already fulfilled?
260	if(expected == future_FULFILLED) return false; // Yes, just return false (didn't block)
261
262	// The future is not fulfilled, try to setup the wait context
263	if(__atomic_compare_exchange_n(&this.ptr, &expected, &wait_ctx, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
264	return true;
265	}
266	}
267	}
268
269	// Stop waiting on a future
270	// When multiple futures are waited for together in "any of" pattern
271	// futures that weren't fulfilled before the thread woke up
272	// should retract the wait ctx
273	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
274	bool retract( future_t & this, oneshot & wait_ctx ) {
275	struct oneshot * expected = &wait_ctx;
276
277	// attempt to remove the context so it doesn't get consumed.
278	if(__atomic_compare_exchange_n( &this.ptr, &expected, future_ARMED, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
279	// we still have the original context, then no one else saw it
280	return false;
281	}
282
283	// expected == ARMED: future was never actually setup, just return
284	if( expected == future_ARMED ) return false;
285
286	// expected == FULFILLED: the future is ready and the context was fully consumed
287	// the server won't use the pointer again
288	// It is safe to delete (which could happen after the return)
289	if( expected == future_FULFILLED ) return true;
290
291	// expected == PROGRESS: the future is ready but the context hasn't fully been consumed
292	// spin until it is safe to move on
293	if( expected == future_PROGRESS ) {
294	while( this.ptr != future_FULFILLED ) Pause();
295	/* paranoid */ verify( this.ptr == future_FULFILLED );
296	return true;
297	}
298
299	// anything else: the future was setup with a different context ?!?!
300	// something went wrong here, abort
301	abort("Future in unexpected state");
302	}
303
304	// Mark the future as abandoned, meaning it will be deleted by the server
305	bool abandon( future_t & this ) {
306	/* paranoid */ verify( this.ptr != future_ABANDONED );
307
308	// Mark the future as abandonned
309	struct oneshot * got = __atomic_exchange_n( &this.ptr, future_ABANDONED, __ATOMIC_SEQ_CST);
310
311	// If the future isn't already fulfilled, let the server delete it
312	if( got == future_ARMED ) return false;
313
314	// got == PROGRESS: the future is ready but the context hasn't fully been consumed
315	// spin until it is safe to move on
316	if( got == future_PROGRESS ) {
317	while( this.ptr != future_FULFILLED ) Pause();
318	got = future_FULFILLED;
319	}
320
321	// The future is completed delete it now
322	/* paranoid */ verify( this.ptr != future_FULFILLED );
323	free( &this );
324	return true;
325	}
326
327	// from the server side, mark the future as fulfilled
328	// delete it if needed
329	thread$ * fulfil( future_t & this, bool do_unpark = true ) {
330	for() {
331	struct oneshot * expected = this.ptr;
332	// was this abandoned?
333	#if defined(__GNUC__) && __GNUC__ >= 7
334	#pragma GCC diagnostic push
335	#pragma GCC diagnostic ignored "-Wfree-nonheap-object"
336	#endif
337	if( expected == future_ABANDONED ) { free( &this ); return 0p; }
338	#if defined(__GNUC__) && __GNUC__ >= 7
339	#pragma GCC diagnostic pop
340	#endif
341
342	/* paranoid */ verify( expected != future_FULFILLED ); // Future is already fulfilled, should not happen
343	/* paranoid */ verify( expected != future_PROGRESS ); // Future is bein fulfilled by someone else, this is even less supported then the previous case.
344
345	// If there is a wait context, we need to consume it and mark it as consumed after
346	// If there is no context then we can skip the in progress phase
347	struct oneshot * want = expected == future_ARMED ? future_FULFILLED : future_PROGRESS;
348	if(__atomic_compare_exchange_n(&this.ptr, &expected, want, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
349	if( expected == future_ARMED ) { return 0p; }
350	thread$ * ret = post( *expected, do_unpark );
351	__atomic_store_n( &this.ptr, future_FULFILLED, __ATOMIC_SEQ_CST);
352	return ret;
353	}
354	}
355
356	}
357
358	// Wait for the future to be fulfilled
359	bool wait( future_t & this ) {
360	oneshot temp;
361	if( !setup(this, temp) ) return false;
362
363	// Wait context is setup, just wait on it
364	bool ret = wait( temp );
365
366	// Wait for the future to tru
367	while( this.ptr == future_PROGRESS ) Pause();
368	// Make sure the state makes sense
369	// Should be fulfilled, could be in progress but it's out of date if so
370	// since if that is the case, the oneshot was fulfilled (unparking this thread)
371	// and the oneshot should not be needed any more
372	__attribute__((unused)) struct oneshot * was = this.ptr;
373	/* paranoid */ verifyf( was == future_FULFILLED, "Expected this.ptr to be 1p, was %p\n", was );
374
375	// Mark the future as fulfilled, to be consistent
376	// with potential calls to avail
377	// this.ptr = 1p;
378	return ret;
379	}
380
381	// Wait for any future to be fulfilled
382	forall(T& \| sized(T) \| { bool setup( T&, oneshot & ); bool retract( T&, oneshot & ); })
383	T & wait_any( T * futures, size_t num_futures ) {
384	oneshot temp;
385
386	// setup all futures
387	// if any are already satisfied return
388	for ( i; num_futures ) {
389	if( !setup(futures[i], temp) ) return futures[i];
390	}
391
392	// Wait context is setup, just wait on it
393	wait( temp );
394
395	size_t ret;
396	// attempt to retract all futures
397	for ( i; num_futures ) {
398	if ( retract( futures[i], temp ) ) ret = i;
399	}
400
401	return futures[ret];
402	}
403	}
404
405	//-----------------------------------------------------------------------
406	// Statics call at the end of each thread to register statistics
407	#if !defined(__CFA_NO_STATISTICS__)
408	static inline struct __stats_t * __tls_stats() {
409	/* paranoid */ verify( ! __preemption_enabled() );
410	/* paranoid */ verify( kernelTLS().this_stats );
411	return kernelTLS().this_stats;
412	}
413
414	#define __STATS__(in_kernel, ...) { \
415	if( !(in_kernel) ) disable_interrupts(); \
416	with( *__tls_stats() ) { \
417	__VA_ARGS__ \
418	} \
419	if( !(in_kernel) ) enable_interrupts(); \
420	}
421	#if defined(CFA_HAVE_LINUX_IO_URING_H)
422	#define __IO_STATS__(in_kernel, ...) { \
423	if( !(in_kernel) ) disable_interrupts(); \
424	with( *__tls_stats() ) { \
425	__VA_ARGS__ \
426	} \
427	if( !(in_kernel) ) enable_interrupts(); \
428	}
429	#else
430	#define __IO_STATS__(in_kernel, ...)
431	#endif
432	#else
433	#define __STATS__(in_kernel, ...)
434	#define __IO_STATS__(in_kernel, ...)
435	#endif
436	}
437	}
438	#endif

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